A food truck vendor averages 150 tacos sold when the price per taco is $4. A study shows that the average number of tacos will increase by 25 tacos for every $1 that the price per taco is lowered. Which equation models the food truck's average sales in dollars, s , in terms of the price per taco, x? A. s=25x+250 B. s=-25x+250 C. s=25x^2+250x D. s=-25x^2+250x